Fuel filter and vapor separator



April 24, 1962 E. P. WISE FUEL FILTER AND VAPOR SEPARATOR Filed July 30, 1958 2 She ets-She'et 1 INENTOR EUGENE P W sE IMWW biy ,vrr'fllfi 3 ,@3 1,019 Patented Apr. 24, 1 962 3,031,010 FUEL FILTER AND VAPOR SEPARATOR Eugene P. Wise, Bloomfield Hills, Mich, assignor to Chrysler Corporation, Highland Park, Mich, a corporation of Delaware Filed July 30, 1958, Ser. No. 752,005 5 Claims. (Cl. 15836.3)

This invention relates to a fuel injection system of the type disclosed in the following related copending applications owned by applicants assignee and having the following filing dates: Thomas M. Ball et 211., Serial No.

751,999, filed July 30, 1958; Clifton M. Elliott, Serial No. 752,004, filed July 30, 1958; John W. Hurst, Serial No. 752,003, filed July 30, 1958, now Patent No. 2,954,- 021, and Clifton M. Elliott, Serial No. 752,000; filed July 30, 1958, now Patent No. 2,957,466.

This invention is concerned in particular with the structure of a combination fuel filter and vapor separator for use in the aforementioned fuel injection system and with the arrangement thereof in said system.

It is customary in fuel injection systems to provide some device to precisely meter the exact fuel requirements to the engine. These devices may be fuel metering valves of the type disclosed in the above mentioned system which valves are designed to adjust the flow of fuel to the engine according to the pressure of liquid fuel in the fuel conduits of the system. With such valves the pressure of fuel vapor in the fuel conduits of these systems is transmitted to said valves and causes them to meter an erroneous quantity of liquid fuel to the engine. Moreover, since the volume of fuel vapor is many times greater than an equivalent amount of liquid fuel, any increase in the amount of vapor present in the conduits of the system will magnify exponentially the error of the fuel metering valves. This error in fuel metering results in a loss of engine power through improper fuel to air ratio and is particularly prevalent on hot days and during engine operating conditions of light load when the fuel pressure in the system is ordinarily not high enough to retard the formation of fuel vapor therein.

An object of this invention is to provide a fuel injection system with a device for separating vapor bubbles and foreign matter from the fuel before the fuel is metered.

Another object is to provide a fuel injection system having a return flow speed metering and load metering unit with a fuel vapor separator device to separate said vapor from the fuel before it passes to the load metering unit.

Another object is to provide the speed chamber of a fuel metering unit with a vapor separator located at such a position within the speed chamber that fuel vapor will be caused to rise to the top of said chamber.

Another object is to provide a vapor separator for the speed chamber of a fuel metering unit, said separator being of sufficient size with respect to the fuel inlet into said chamber to slightly decrease the pressure of and slow down the flow of fuel coming into said chamber sulficiently to cause any vapor entrapped in the fuel to rise to the top of the chamber.

In carrying out this invention a fuel feed conduit is connected at one end to a fuel source which supplies a substantially constant volume of fuel under pressure to said fuel feed conduit and communicates at its other end with the cylinders of an internal combustion engine. A return fuel flow conduit is connected at one end to the fuel feed conduit at a point intermediate said fuel source and said engine and at the other end to said fuel source to provide a continuous bypass of a portion of the fuel supplied to said fuel feed conduit back to said fuel source. The continuous flow of fuel from the fuel source to the fuel feed conduit to the return fuel flow conduit and back to the fuel source continuously purges a major portion of fuel vapor developed in the fuel source and said conduits from the fuel which is to be subsequently quantitatively metered to the engine. The vapor which is carried back to the fuel source will rise to the top of the fuel sump or tank and escape through suitable vapor bleed apertures therein. To facilitate the escape of vapor, the return fuel cflow conduit may be connected to the top of said tank to dump the return fuel and vapor at the top of the liquid fuel supply in the tank.

Disposed in the return fuel flow conduit is a valve which regulates the flow of liquid back to the tank. This valve is partially operated or adjusted by a pressure sensitive element which operatively communicate with the fuel in the fuel feed conduit and is designed to adjust the valve in response to the pressure of the liquid portion of the fuel in the conduit. This element is not designed, however, to differentiate between the pressure of the liquid feed fuel and the pressure of the vaporized feed fuel and the presence of fuel vapor in the feed fuel in quantities too great to be purged by the return fuel flow causes an erroneous adjustment of the valve by said element.

To facilitate the removal of this vapor from the feed fuel by the return fuel fiow conduit the present invention provides a means to separate the vapor from the feed fuel and direct the vapor into the return fuel flow conduit. This is accomplished by providing a chamber in the fuel feed conduit, said chamber having a fuel outlet at its lower portion communicating with the engine and having a fuel outlet at its mid portion communicating with the return fuel feed conduit. The fuel source is connected to a fuel inlet at the topmost portion of the chamber. An elongated cylinder of fine mesh wire or organic material closed at its bottom is connected at its top to the fuel inlet at the top of the chamber. This cylinder has a diameter considerably larger than the fuel inlet and is positioned upright in the chamber with its lower portion adjacent the fuel outlet at the lower portion of the chamber and with its upper portion lying above the return flow orifice.

The vapor supplied to the cylinder from the fuel source being lighter than the liquid fuel in the cylinder tends to rise to the top of the cylinder and pass out through the upper portion thereof into the path of flow of the return fuel. This vapor rise is facilitated and aided by the slowing down of the feed fuel as it passes from the fuel inlet at the top of the chamber into the larger cavity of the cylinder. The heavier liquid fuel passes out of the lower portion of the cylinder and out through the fuel outlet at the lower portion of the chamber to the engine.

Further objects and advantages and description of this invention will be apparent from the following detailed illustration thereof, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views:

FIGURE 1 is a side elevational view of the fuel injection metering unit;

FIGURE 2 is substantially a vertical longitudinal midsectional view through the unit of FIGURE 1;

FIGURE 3 is a horizontal sectional view of the unit taken on line 3-3 of FIGURE 1, and rotated counterclockwise FIGURE 4 is a vertical sectional view of the unit of FIGURE 1 taken along a line and in the direction corresponding to 44 of FIGURE 3;

FIGURE 5 is a vertical sectional view of the load sensor of FIGURE 1 taken along a line corresponding to 5-5 of FIGURE 3 in the direction of the arrows with wall portions removed below line L to show a section of the load metering orifice and needle of the unit FIG- 3 URE 1 taken along a line corresponding to 5A5A of FIGURE 3 in the direction of the arrows;

FIGURE 6 is a view partly in cross section of the general arrangement of the fuel injection system and the engine; and

FIGURE 7 is a side elevational view of an automotive distributor for driving the unit of FIGURE 1.

Referring in detail to the drawings, and in particular to FIGURES 1 and 2, a fuel injection metering unit designated generally as 10 is provided with a speed sensor designated generally as 12. This speed sensor is conveniently divided into three sections, a speed section 14, an intermediate section 16, and a governor section 18. All three of these sections cooperate simultaneously to adjust the amount of fuel available to the engine in accordance with the fuel requirements of the engine as related to engine speed.

Referring to FIGURES 2 and 3, the speed section 14 comprises a housing 20 having a chamber 22 therein, said chamber having a fuel outlet 34 at its lower portion and having a fuel outlet or return flow metering orifice 30 at its mid portion. Outlet 34 communicates with chamber 36 of a load sensor 38 (see FIGURE 5) which chamber 36 is located on the upstream side of the load metering orifice 154. A fuel inlet 27 at the top of the chamber 22 connects to a fuel supply 198 through conduit 26 and to a fine wire or organic material mesh cylinder 28 located upright in chamber 22. Cylinder 28 provides a combination fuel filter and vapor separator for the fuel feed system. This cylinder receives a substantially constant supply of fuel under pressure from tank 198 and fuel pump 24 which pump may be electrically driven at a speed independent of the speed of the engine. The lower portion of cylinder 28 is located adjacent the fuel outlet 34 at the lower portion of chamber 22 and the upper portion of said cylinder is located adjacent the fuel outlet or return flow metering orifice 30 and communicates with the flow stream of the return fuel flowing from the cylinder to the return flow metering orifice 30. Orifice 30 provides a passage from chamber 22 to a return flow conduit 32 which winds throughout the unit 10 and provides numerous chambers designated 32 as shown in FIGURES 2, 4, and 5.

The diameter of cylinder 28 is considerably larger than inlet 27 and causes a fuel kinetic pressure or velocity drop across inlet 27 and a corresponding slowing down of the fuel flow in cylinder 28. Fuel flowing into cylin der 28 from tank 198 may contain a large amount of fuel vapor picked up from the return flow fuel or created in the tank. This vapor will have a tendency to rise to the upper portion of cylinder 28 due to the decrease in fuel flow speed in said cylinder. As the vapor rises it passes out of the cylinder into the return flow stream and back to the tank. The liquid fuel being heavier will pass out of the lower portion of the cylinder and out through outlet 34 into chamber 36.

The intermediate section 16 of the speed sensor 12 is separated from the speed section 14 and the governor section 18 by diaphragms 42 and 44 respectively. This section is provided with a housing 45 having a chamber 46 which communicates with the downstream chamber 48 of the load sensor 38 through a conduit 50 to provide equal fuel pressures in chambers 46 and 48 for a purpose to be explained below.

A chamber 52 in section 16 communicates with an intake manifold 54 of the engine at a point adjacent the throttle valve 56 through conduit 58 (FIGURES 2 and 6) and provides a substantially constant low pressure to the diaphragm 44 when the engine is idling and also provides an increased pressure when the throttle 56 is opened (see FIGURE 6). Conduit 58 also serves to convey fuel passing the seals 64 to the intake manifold. An air bleed 57 communicating with chamber 52 allows air under atmospheric pressure to bleed said chamber to partially offset the low pressure therein and provides a means for adjusting the idling mixture of the engine. This bleed is of such a size as to adjust but not eliminate the vacuum in chamber 56. A conventional needle valve 60 threadably received in housing 45 and adjustable with respect to the opening of conduit 58 into chamber 52 provides a means to regulate the amount of vacuum transmitted to chamber 52 from the engine manifold in order to further regulate the idling speed of the engine.

Referring again to FIGURE 2, a fuel return flow metering shaft 62 slidably mounted in housing 45 and provided with sliding sealisng rings 64 is secured at one end to diaphragm 42 and valve disc 66 by flanges 65 and 68 and rivets 70. Disc 66 is movable with shaft 62 toward orifice 30 to retard the flow of return fuel therethrough to return flow conduit 32. By using a disc type metering valve, a large flow rate can be obtained by relatively small longitudinal movement of the metering shaft 62 which renders the speed sensor more sensitive to speed and pressure variations. A split retaining ring 72 positioned in a circumferential groove 74 in shaft 62 provides a stop to prevent valve disc 66 from moving too far from orifice 30. The other end of shaft 62 is connected to diaphragm 44 by flanges 74 and 76 and rivets 78.

Governor section 18 of the speed sensor comprises a housing 80 having a chamber 82 therein communicating with one side of diaphragm 44. The pressure in this chamber is at all times atmospheric and therefore allows a pressure differential to exist across diaphragm 44, since chamber 52 communicates at all times with the low pressure portion of the engine intake manifold. A shaft 84 is rotatably mounted in a sleeve member 81 in housing 80 by ball bearing 86 and bearing surface 87 on sleeve 81 and is keyed for rotation to a flexible drive shaft 88 of the engine distributor 89 (FIGURE 7) by key 90 on shaft 88 and slot 91 in shaft 84. The chamber 92 formed between member 81 and housing 80 serves as a lubricating oil reservoir for ball bearing 86 and bearing surface 87. The oil is introduced into oil cup 94 and flows to said ball bearing surface through apertures 96 in member 81.

An end of member 81 is threadably received in the end of housing 80 and is secured against rotatable movement therein by lock nut 98 threadably received on said end of member 81 and threaded into tight engagement with the end face 100 of housing 80. A nut 102 is threadably received on the end of housing 80 and secures the flexible drive shaft covering 104 to said housing. A bifurcated flyweight support 106 is secured to shaft 84 for rotation therewith and pivotally supports flyweights 108 and 110 on bearing lugs 112 and 114 respectively extending between the sides of the bifurcated support 106. A sleeve 116 having a flange 118 thereon is mounted on a reduced portion of shaft 84 and is slidable longitudinally of said portion. Slots 120 and 122 in flyweights 108 and 110 respectively loosely receive flange 118 which is abutted by shoulders 124 and 126 on flyweights 108 and 110 respectively. A sleeve 128 also longitudinally slidably mounted on said reduced portion of shaft 84 is frictionally secured at one end to the inner race of a ball bearing 130. Said sleeve 128 mounts on its other end a spring 132 which resiliently urges said sleeves 116 and 128 apart and causes the outer race of ball bearing 130 to abut the heads of rivets 78 with sufficient force to prevent the outer race from rotating with the inner race and shaft 84. The rotation of shaft 84 in response to the rotation of the flexible drive shaft 88 causes the flyweights 108 and 110 to pivot outwardly from shaft 84 around bearings 112 and 114 respectively, which brings shoulders 124 and 126 of the flyweights into contact with the flange 116 and tends to urge the latter against spring 132. The force transmitted to spring 132 is transmitted through the connected diaphragms to the return flow metering valve disc 66 and tends to move said disc closer to the orifice 30.

It is noted that the force output of a fiyweight governor is, mathematically speaking, proportional to the square of the engine speed. Such a relationship between engine speed and force output, however, does not suffice for supplying fuel to the engine in accordance with the present metering unit since the air consumption of an internal combustion engine with respect to engine speed deviates from a linear relationship. This deviation is particularly noticeable in engines utilizing the conventional ram type manifolds of the type shown for example in Patent 2,791,205 of which are long enough to develop air pulsations therein which pulsations ram additional air into the engine cylinders and cause the engine to require more fuel to offset the leaning effect of the additional air. The relationship therefore between engine speed and governor force output is changed herein by the interposition of spring 132 between sleeves 116 and 128. This spring allows the radius of rotation of the centers of gravity of the flyweights to increase at a faster than normal rate with respect to engine speed over a portion of the speed range and to thereby exert a force on the spring, sleeve 128, and valve shaft 62 which force results in an increase in fuel flow to the engine over the amount which would flow at that speed in the absence of the spring. Spring 132 may also be designed to have a variable spring rate should it be desired to further vary the output force of the flyweights. At high speed ranges during which the proportion of air consumption to engine speed decreases due to a reduction in the ram effect at said speeds, the sleeves 116 and 128 will abut each other and the radius of rotation of the centers of gravity of the fiyweights will increase with further increases in engine speed at the normal or lower rate. This reduced rate of said radius increase will result in the force output of the governor also increasing at said normal or lower rate with respect to said further increase in engine speed, which reduced rate of force output will result in a flow of fuel to the engine which corresponds more nearly to the linear air consumption of said engine at high speeds.

The specific structure of the load sensor 3 8 with which the fuel outlet 34 of chamber 22 communicates is shown in FIGURE 3. The load sensor is conveniently divided into three sections for purposes of description. The first section 150 contains the mechanisms which are responsive to changes in manifold pressure and changes in atmospheric conditions to move through suitable linkages the load metering needle 152 with respect to the load metering orifice 154. This first section 150 comprises a cylinder 156 (FIGURES 3 and 5) having a manifold pressure inlet 158 which is operatively connected to the low pressure portion of the engine intake manifold 220. As shown in FIGURE 6, this portion may conveniently be chamber 54 which is downstream of primary throttle valve 56. A piston 160 having circumferential dirt catching grooves 162 thereon is reciprocably mounted in cylinder 156 and moves upwardly against spring 164 as the intake manifold pressure decreases. The increments of movement of piston 160 are substantially linear with respect to the incremental changes in intake manifold pressure and provide a convenient basis for the design of the load metering needle 152 and orifice 154 which design must be such so as to obtain desired flow characteristics across said orifices. The degree of the taper of needle 152, the length of the stroke of piston 160, and the size of orifice 154 are interrelated and are specifically predetermined. These dimensions must be such that the flow of fuel across orifice 154 can always be adjusted by the load sensor over the speed range of the engine to be substantially linear with respect to the total air how to the engine as measured by the load sensor. An air vent 159 communicating with conduit 58 in intermediate section 16 of the speed sensor through suitable conduit means 159 cast or drilled in sections 14 and 16 (FIGURES 2 and 3) is provided in the housing of section 150 and allows atmospheric air to flow through slits 161 in the piston 160 and into contact with the exterior of air tight bellows 166 which is nested within the lower portion of piston 160. The low pressure in conduit 58 sucks a continuous flow of air past the bellows 166 which bellows expands lengthwise in response to either a drop in atmospheric pressure or an increase in atmospheric temperature and conversely contracts lengthwise in response to increased atmospheric pressure or decreased atmospheric temperature. Said bellows is secured at its top end to a shell 168 having a plurality of circumferentially spaced slots 170 therein through which slidably extend fingers 172 of plate 174 to which the lower end of bellows 166 is secured. Fingers 172 of plate 174 fit into grooves in the inner wall of piston 160 and are retained therein by split retaining ring 17 6. A spring 177 normally urges bellows 166 to a contracted condition. A plate 178 is secured to the lower end of shell 168 and carries a socket 180 into which a ball 182 of linkage member 184 is retained. Said linkage member is pivotally secured to arm 186 which is pivotally attached to one end of shaft 188 which shaft is rotatably mounted in the housing of section 150 and extends into chamber 36 of the second section 196 of the load sensor. An arm 190 secured to the other end of shaft 188 is pivotally connected to the load metering needle 152. An arm 192 secured to shaft 138 adjacent the arm 186 is provided with a set screw 194 which extends through slot 196 in arm 186. Arms 186 and 192 may be moved relative to each other when the set screw is loose to adjust the position of the metering needle 152 with respect to orifice 154 at any desired operating condition of the load sensor, after which the set screw is tightened.

The second section 197 of the load sensor is separated from the first section 150 by suitable walls and fluid tight seals which keep the fluid in upstream chamber 36 of section 197 from entering section 150. Chamber 36 receives its fuel supply from outlet 34 of chamber 22 of the speed section of the speed sensor which fuel represents the portion of the pumped fuel that is not returned to the fuel tank 198 (FIGURE 6) through the return flow conduit 32. Orifice 154 in the housing of chamber 136 opens into the downstream chamber 48 of the third section 2110 of the load sensor. The total effect of the intake manifold pressure and the pressure and temperature of the atmosphere regulates the positioning of the metering needle 152 with respect to orifice 154 to control the flow of fuel therethrough into chamber 48.

Referring to FIGURES 3 and 4, a pressure valve needle 2112 positioned in chamber '48 is attached to a diaphragm 2M and is normally urged to a closed position with respect to a fuel port 206 which communicates with the fuel distribution chamber 268 of rosette 210. The combined pressures exerted by the return fuel in conduit 32 and spring 212 urge needle 202 to its normally closed position. These pressures can be overcome by the pressure of the fuel flowing into chamber 48 when a predetermined minimum pressure of fuel in chamber 43 is attained. By establishing this minimum pressure in chamber 43 the formation of vapor in said chamber and in the rest of the system is retarded especially during starting and at slow engine speeds and the proper flow of fuel through the return flow conduit is insured since the resistance to said flow is overcome by the minimum pressure.

The rosette 210 in FIGURE 4 comprises a body 213 having a plurality of apertures 214 communicating with fuel chamber 208 across orifices 216. A nozzle feed conduit 218 is secured in each said aperture and communicates with a particular portion of the engine intake manifold 220 through a fuel injection nozzle 222 (FIGURE 6). An air conduit 224 has a threaded bushing 225 secured thereto which is threadably secured to body 213 by an intermediate valve carrying nut 227. A lock nut 229 secures the fuel feed conduit retaining plate 231 to the body 213 which plate urges the enlarged portions 233 of the nozzle feed conduits inwardly of the rosette to retain said conduits therein (see FIGURE 5). Conduit 224 may be connected to an air pump 226 which is suitably mounted on the engine block 228 and actuated by the engine camshaft 230 (FIGURE 6). The use of this air pump is optional, however a better control over the fuel atomization and dispersion has been obtained by using the pump and its use is advisable. A disc valve 232 normally urged against the inlet air port 234 of said rosette by spring 235 will prevent fuel from flowing into conduit 224 should something happen to the system to cause the fuel in the nozzle feed conduits to back up through orifices 240. Slots 238 in a valve retaining plate 239 permit the air to fiow into chamber 236 after it passes through port 234. Air chamber 236 communicates with each said aperture 214 across orifices 240. As the air flows across orifices 240 it mixes with the fuel flowing across orifices 216 and forms a liquid in air type dispersion which then flows through the nozzle feed conduits to the fuel injection nozzles. It is noted that the close proximity of the orifices 216 and 249 prevents collection of liquid fuel on the downstream side of orifice 216. The air orifices 240 should be larger than the fuel orifices 216 since at idle and low fuel consumption conditions the volume of air used greatly exceeds the volume of fuel used.

Referring further to FIGURE 4 a cylinder 242 positioned in the return flow conduit 32 slidably receives an accelerator piston 244. Attached to the piston is a shaft 246 which is slidably received in a recess 248 in shaft 250. A groove 252 in shaft 246 slidably receives a screw 254 which limits the longitudinal movement of the shaft 246 and attached piston 244. An arm 254 is secured to shaft 250 at one end and to shaft 256 at its other end, which shaft 256 is operatively connected to the engine accelerator pedal and rotates clockwise in response to the depression of the pedal to urge shaft 250 against spring 258 to move piston 244 downward. As said piston is moved downward it forces fuel trapped in accelerator chamber 260 through conduit 262 and into chamber 264 where it exerts a force on diaphragm 266. When the pressure exerted on said diaphragm by the accelerator pump reaches a predetermined minimum, needle valve 268 will open and allow accelerator fuel to flow directly through conduit 269 to chamber 208 of the rosette for distribution to the fuel injection nozzles. A ball check valve 270 separating the return flow conduit 32 from the accelerator chamber 260 is drawn upwardly from port 272 as piston 244 moves upwardly in response to engine deceleration and allows return fuel to fill chamber 260. The downward movement of piston 244 closes port 272 by forcing ball 270 into contact therewith. It is noted that a spring 274 and return fuel in return flow conduit 32 cooperate to urge diaphragm 266 and attached needle valve 268 to a closed position and establish the minimum pressure on diaphragm 266 which must be overcome by the pressure exerted by piston 244 on accelerator fuel within chamber 260 if acceleration fuel is to flow to the rosette. This accelerator pump is actuated in response to each depression of the accelerator pedal to deliver an extra amount of fuel to the engine While the rest of the fuel distribution system is catching up to the increased engine load condition. Without said pump the rapid increase in air flow into the intake manifold as the throttle is opened would cause a lean air-fuel mixture and result in coughing and spitting of the engine. By placing the accelerator pump in the return flow conduit the fuel which is drawn into the pump is kept cool by the continuous passage of return fuel around the cylinder 242 and, in addition, any vapor drawn into said cylinder can bleed out through the top of the pump around the loose fitting piston and back into the return flow conduit. Also the location of the accelerator pump in the return flow conduit provides a means for rendering leakage of the pump inconsequential.

The operation of the fuel injection metering unit 10 will be described in relation to a change in static engine operating conditions, that is, constant engine speed and load. Under said static operating conditions, the combined forces exerted by fiyweights 108 and 110 and the fuel in chamber 46 is balanced by the force exerted by the fuel in chamber 22 and the return flow metering disc 66 is maintained stationary at a distance away from orifice 30. In this static condition, the amount of fuel delivered to the rosette distributing chamber 208 is constant and is equal to the constant amount of fuel being delivered to the system by the pump less the constant amount of fuel being returned to the fuel tank through the return flow conduit 32. If this static condition represents the engine during normal driving speed when throttle blade 56 is substantially open, the pressure in chamber 52 has no noticeable effect on the operation of the uni-t and may be disregarded. It is only during idling and very low engine speeds when the throttle blade 56 is substantially closed that the pressure differential across diaphragm 44 becomes significant.

In order to increase engine output at constant engine speed, such as is necessary to maintain constant car speed when starting up a hill, the throttle valve 56 is moved to a more open position by depression of the car accelerator pedal. The increase in manifold pressure that results is accompanied by an increase in air flow rate that must be matched by a proportionate increase in fuel flow. This is accomplished by transmission of the increased manifold pressure to the load sensor piston through conduit 153 thereby moving said piston downwardly to move the load metering needle 1 52 to a more open position with respect to the load metering orifice 154. The fuel flow across said orifice and to the engine is consequently increased. This increased fuel flow tends to reduce the pressure in chambers 22 and 36 causing the return flow metering disc 66 to be urged closer to orifice 30 further restricting the amount of flow returned to the fuel tank and maintaining the balance of forces between the fuel pressure in chambers 46 and 22 substantially equal to the force exerted by the fiyweights 108 and 110.

As the engine speed is increased or decreased at any given manifold pressure, the force output of said flyweight will also increase or decrease as a function thereof. This will cause the force against return flow metering disc to vary in the same amount, urging the return flow metering disc toward orifice 30 to a greater or lesser degree. The resulting return flow restriction in each case will cause a pressure differential across diaphragm 42 between chambers 46 and 22 to develop sufficiently to balance the flyweight output force. Since said pressure differential is also applied across the load metering orifice 154, the flow through said orifice also is a function of engine speed.

As a result of the above-described load influence on the load metering needle position, and the speed influence on the pressure differential across the load metering orifice, the fuel flow of the fuel injection metering unit can be tailored, through calibration procedure, to satisfy the engine demand.

I claim:

1. In a fuel metering unit of a fuel injection system for an internal combustion engine, a speed chamber having at its lower portion a fuel outlet adapted for communication with said engine, said chamber communicating with a fuel return flow metering orifice located above said fuel outlet, means responsive to engine operating conditions for adjusting the flow through said return fiow metering orifice, a fuel feed conduit in communication with a pressure fuel source, an elongated hollow filter positioned upright in said speed chamber and connected at its top to said fuel feed conduit to receive fuel therefrom, said filter comprising a cylindrical screen of fine mesh metal wire and having a considerably larger diameter than said fuel feed conduit to substantially reduce the speed of the incoming fuel, the upper portion of said filter lying substantially above the horizontal plane of said return flow orifice, and the lower portion of said filter lying substantially in the horizontal plane of said fuel outlet.

2. In a fuel metering unit of a fuel injection system for an internal combustion engine, said unit having a speed chamber communicating at a lower portion thereof with a fuel distribution chamber across a load metering orifice and communicating at a higher portion thereof with a return flow conduit across a return fiow metering orifice, said unit also having a speed responsive metering member shiftable with respect to said return flow orifice to adjust the flow of return fuel therethrough in accordance with engine speed, a fuel feed conduit in communication with a pressure fuel source, an elongated mesh filter positioned upright in said speed chamber and connected at its top to said fuel feed conduit to receive fuel therefrom, said filter having a considerably larger diameter than said fuel feed conduit to substantially reduce the speed of the incoming fuel, the upper portion of said filter being above the horizontal plane of said return flow orifice, and the lower portion of said filter being adjacent said load metering orifice.

3. In a fuel metering unit of a fuel injection system for an internal combustion engine, a pressure fuel source, a speed chamber having at its lower portion a fuel outlet for connection to said engine, a fuel return flow metering orifice connecting said speed chamber with said pressure fuel source to return fuel to the latter, a fuel feed conduit in communication with said pressure fuel source, an elongated hollow filter positioned upright in said speed chamber and connected at its top to said fuel feed conduit to receive fuel therefrom, said filter having a fine mesh; chamber of a considerably larger diameter than said fuel feed conduit to substantially reduce the speed of the incoming fuel, the upper end of said filter being above the level of said return flow orifice and the lower end of said filter being adjacent the level of said fuel outlet, and means responsive to engine operating conditions for regulating the rate of fuel flow through said return flow metering orifice.

4. In a fuel metering unit of a fuel injection system for an internal combustion engine, a pressure fuel source, a speed chamber having at its lower portion a fuel outlet for connection to said engine, a fuel return flow metering orifice connecting said speed chamber with said pressure fuel source to return fuel to the latter, .a fuel feed conduit in communication with said pressure fuel source, an elongated hollow filter positioned upright in said speed chamber and connected at its top to said fuel feed conduit to receive fuel therefrom, said filter having a fine mesh chamber of a considerably larger diameter than said fuel feed conduit to substantially reduce the speed of the incoming fuel, the upper end of said filter being above the level of said return flow orifice and the lower end of said filter being adjacent the level of said fuel outlet, and means responsive to engine speed for regulating the rate of fuel flow through said return flow metering orifice as an inverse function of engine speed.

5. In a fuel metering unit of a fuel injection system for an internal combustion engine, a pressure fuel source, a speed chamber having at its lower portion a fuel outlet adapted to communicate With said engine across a load metering orifice, fuel return flow metering means communicating with said speed chamber for bypassing said engine, a fuel feed conduit in communication with said pressure fuel source, an elongated hollow filter positioned upright in said speed chamber and connected at its top to said fuel feed conduit to receive fuel therefrom, said filter having a fine mesh chamber of a considerably larger diameter than said fuel feed conduit to substantially reduce the speed of the incoming fuel, the upper end of said filter being above the level of said return flow orifice and the lower end of said filter being adjacent the level of said fuel outlet, and means responsive to engine speed for regulating the rate of fuel flow through said return flow metering means as an inverse function of engine speed.

References Cited in the file of this patent UNITED STATES PATENTS 1,623,074 Tartrais Apr. 5, 1927 1,840,079 Bradley Jan. 5, 1932 1,849,590 Phillips Mar. 15, 1939. 1,895,119 Arthur Jan. 24, 1933 2,412,289 Pugh et a1 Dec. 10, 1946 2,727,503 Reiners Dec. 20, 1955 

